CN109575286B

CN109575286B - Polyamide-imide film and preparation method thereof

Info

Publication number: CN109575286B
Application number: CN201811594903.1A
Authority: CN
Inventors: 金善焕; 吴大成; 李辰雨; 郑多宇; 林东真; 崔经园
Original assignee: SKC Co Ltd
Current assignee: Aisikai Mcwoo Co ltd
Priority date: 2017-12-28
Filing date: 2018-12-25
Publication date: 2021-11-09
Anticipated expiration: 2038-12-25
Also published as: JP2019151818A; CN113801323B; CN109575286A; TW201930418A; TWI710588B; US20190202990A1; JP2021165399A; KR102091559B1; JP7345247B2; CN113801323A; KR20190080426A; EP3505558A1; EP3505558B1; US11365287B2

Abstract

Embodiments of the present application relate to a method of preparing a polyamideimide film and a polyamideimide film prepared thereby. The method comprises the following steps: mixing and reacting a diamine compound, a dianhydride compound, and a dicarbonyl compound simultaneously or sequentially in an organic solvent in a polymerization apparatus to prepare a polymer solution; transferring the polymer solution to a tank; purging the tank with an inert gas; casting the polymer solution in the tank onto a belt and then drying it to prepare a gel sheet; heat-treating the gel sheet while it is moving to prepare a cured film; cooling the solidified film while it is moving; winding the cooled cured film with a winder. The method can prepare the polyamide-imide film with excellent optical property and mechanical property.

Description

Polyamide-imide film and preparation method thereof

Technical Field

Embodiments relate to a method of preparing a polyamideimide film. The method can prepare the polyamide-imide film with excellent optical property and mechanical property.

Background

Polyamide-imide (PAI) is used in applications such as primary electrical insulation, coatings, adhesives, extruded resins, heat-resistant paints, heat-resistant sheets, heat-resistant adhesives, heat-resistant fibers, and heat-resistant films because of its excellent abrasion resistance, heat resistance, and chemical resistance.

Polyamideimides are used in various fields. For example, polyamideimide is made in powder form and used as a coating for metal or magnet wire. It may be mixed with other additives according to its use. In addition, polyamideimides can be used as corrosion-inhibiting decorative coatings with fluoropolymers. It can be used to bond fluoropolymers to metal substrates. In addition, due to its heat and chemical resistance, polyamideimide is used as a gas separation membrane for coating kitchen utensils, and in a natural gas well to filter contaminants and impurities such as carbon dioxide, hydrogen sulfide, etc.

In recent years, polyamideimides have been developed in the form of thin films, which are cheaper and have excellent optical, mechanical and thermal properties.

Disclosure of the invention

Technical problem

One embodiment is directed to providing an optimum method for producing a polyamideimide film which is colorless and transparent and has excellent mechanical properties.

In addition, another embodiment is directed to a polyamideimide film prepared by the above preparation method and its use.

Problem solving scheme

In one embodiment, there is provided a method for preparing a polyamideimide film, the method comprising: mixing and reacting a diamine compound, a dianhydride compound, and a dicarbonyl compound simultaneously or sequentially in an organic solvent in a polymerization apparatus to prepare a polymer solution; transferring the polymer solution to a tank; purging the tank with an inert gas; casting the polymer solution in the tank onto a belt and then drying it to prepare a gel sheet; heat-treating the gel sheet while it is moving to prepare a cured film; cooling the solidified film while it is moving; winding the cooled cured film with a winder.

In another embodiment, there is provided a polyamideimide film produced by the above-described method of producing a polyamideimide film.

Advantageous effects of the invention

The method for producing a polyamideimide film can ensure high processing efficiency, reduce the defect rate of the polyamideimide film produced therefrom, and impart excellent properties in terms of optical properties and mechanical properties.

Drawings

FIG. 1 is a schematic flow diagram of a method of making a polyamideimide film according to one embodiment.

FIG. 2 schematically illustrates process equipment for preparing a polyamideimide film according to one embodiment.

Best mode for carrying out the invention

Hereinafter, the present invention is described in detail by referring to examples. The embodiments are not limited by the following disclosure. On the contrary, they can be modified into various forms as long as they do not change the gist of the present invention.

Some regions or thicknesses may be exaggerated for clarity in illustrating various layers and regions in the drawings. In the drawings, the thickness of some layers and regions are exaggerated for convenience of illustration. Like reference numerals refer to like elements throughout the specification.

It should be understood that when a component is referred to as "comprising" an element in this specification, the component may also comprise other elements unless stated otherwise.

In addition, unless otherwise indicated, all numbers and expressions referring to quantities of ingredients, reaction conditions, and the like, used herein are to be understood as modified by the term "about.

The terms first, second, etc. are used herein to describe various elements, and the elements should not be limited by these terms. These terms are only used to distinguish one element from another.

In addition, the term "substituted" as used herein means substituted with at least one substituent selected from the group consisting of deuterium, -F, -Cl, -Br, -I, hydroxyl, cyano, nitro, amino, amidino, hydrazine, hydrazone, ester, ketone, carboxyl, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkoxy, substituted or unsubstituted alicyclic organic group, substituted or unsubstituted heterocyclic group, substituted or unsubstituted aryl group and substituted or unsubstituted heteroaryl group. The substituents listed above may be linked to each other to form a ring.

One embodiment provides a method of making a polyamideimide film.

Referring to fig. 1, the method of preparing a polyamideimide film includes: mixing and reacting a diamine compound, a dianhydride compound, and a dicarbonyl compound simultaneously or sequentially in an organic solvent in a polymerization apparatus to prepare a polymer solution (S100); transferring the polymer solution into a tank (S200); purging the tank with an inert gas (S300); casting the polymer solution in the tank onto a belt and then drying it to prepare a gel sheet (S400); heat-treating the gel sheet while it is moving to prepare a cured film (S500); cooling the solidified film while it is moving (S600); the cooled cured film is wound up using a winder (S700).

The polyamideimide thin film is a film mainly composed of a polyamideimide resin. The polyamideimide resin contains amide repeating units and imide repeating units as structural units in a predetermined molar ratio.

In the method for preparing a polyamideimide film, a polymer solution for preparing a polyamideimide resin is prepared by mixing and reacting a diamine compound, a dianhydride compound and a dicarbonyl compound in an organic solvent simultaneously or sequentially in a polymerization apparatus (S100).

In one embodiment, the polymer solution may be prepared by simultaneously mixing and reacting a diamine compound, a dianhydride compound, and a dicarbonyl compound in an organic solvent.

In another embodiment, the step of preparing the polymer solution may comprise: firstly, mixing and reacting a diamine compound and a dianhydride compound to prepare a polyamic acid (PAA) solution; next, a polyamic acid (PAA) solution and a dicarbonyl compound are mixed and reacted to simultaneously form an amide bond and an imide bond. The polyamic acid solution is a solution containing polyamic acid.

In another embodiment, the step of preparing the polymer solution may comprise: firstly, mixing and reacting a diamine compound and a dianhydride compound to prepare a polyamic acid (PAA) solution; dehydrating the polyamic acid solution to prepare a Polyimide (PI) solution; secondly, the Polyimide (PI) solution and the dicarbonyl compound are mixed and reacted to further form an amide bond. The polyimide solution is a solution containing a polymer having imide repeating units.

In another embodiment, the step of preparing the polymer solution may comprise: firstly, mixing and reacting diamine compound and dicarbonyl compound to prepare Polyamide (PA) solution; next, the PA solution and the dianhydride compound are mixed and reacted to further form an imide bond. The polyamide solution is a solution comprising a polymer having amide repeating units.

The polymer solution thus prepared may be a solution including a polymer containing at least one selected from the group consisting of a polyamic acid (PAA) repeating unit, a Polyamide (PA) repeating unit, and a Polyimide (PI) repeating unit.

Alternatively, the polymer contained in the polymer solution contains imide repeating units derived from polymerization of a diamine compound and a dianhydride compound and amide repeating units derived from polymerization of a diamine compound and a dicarbonyl compound.

In one embodiment, the step of preparing the polymer solution may further comprise introducing a catalyst.

The catalyst may include, for example, beta-picoline or acetic anhydride, but is not limited thereto. Further addition of the catalyst can accelerate the reaction rate and enhance the chemical bonding force between or within the repeating units.

In one embodiment, the step of preparing the polymer solution may further comprise adjusting the viscosity of the polymer solution.

Specifically, the step of preparing the polymer solution may include: (a) mixing and reacting a diamine compound, a dianhydride compound, and a dicarbonyl compound simultaneously or sequentially in an organic solvent to prepare a first polymer solution; (b) measuring the viscosity of the first polymer solution and assessing whether a target viscosity is reached; (c) if the viscosity of the first polymer solution does not reach the target viscosity, a dicarbonyl compound is further added to produce a second polymer solution having the target viscosity.

The target viscosity may be 100000cps to 500000cps at room temperature. Specifically, the target viscosity may be 100000cps to 400000cps, 100000cps to 350000cps, 100000cps to 300000cps, 150000cps to 300000cps, or 150000cps to 250000cps, but is not limited thereto.

In another embodiment, the polymer solution may contain a solid content of 10% to 20% by weight. Specifically, the solid content contained in the second polymer solution may be 12% to 18% by weight, but is not limited thereto.

If the solid content contained in the polymer solution is within the above range, a polyamideimide film can be efficiently produced in the extrusion and casting steps. In addition, the polyamide-imide film prepared by the method has improved mechanical properties such as modulus and optical properties such as low yellow index.

In one embodiment, the step of preparing the polymer solution may further comprise adjusting the pH of the polymer solution. In this step, the pH of the polymer solution may be adjusted to 4-7 or 4.5-7.

The pH of the polymer solution may be adjusted by adding a pH adjuster. The pH adjuster is not particularly limited and may include amine compounds such as alkoxyamines, alkylamines, and alkanolamines.

If the pH of the polymer solution is adjusted to the above range, it is possible to prevent damage to equipment in the subsequent process, prevent defects from occurring in the film produced from the polymer solution, and obtain desired yellow index optical properties and desired mechanical properties of modulus.

The pH modifier may be used in a molar amount of 0.1% to 10% based on the total moles of monomers in the polymer solution.

The step of preparing the polymer solution may further comprise purging the tank with an inert gas. The step of purging the can with an inert gas can remove moisture, reduce impurities, improve reaction yield, and impart excellent surface appearance and mechanical properties to the finally produced film.

In this case, the inert gas may be at least one selected from the group consisting of nitrogen, helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn), but is not limited thereto. Specifically, the inert gas may be nitrogen.

The molar ratio of dianhydride compound to dicarbonyl compound used to prepare the polymer solution may be 20:80 to 80:20, for example 20:80 to 50: 50. If the dianhydride compound and the dicarbonyl compound are used in the above molar ratio, it is advantageous to obtain desired mechanical and optical properties of the polyamideimide film prepared from the polymer solution.

The diamine compound is a compound that forms an imide bond with the dianhydride compound and forms an amide bond with the dicarbonyl compound to form a copolymer.

The diamine compound is not particularly limited, but it may be, for example, an aromatic diamine compound containing an aromatic structure. For example, the diamine compound may be a compound represented by the following formula 1.

[ formula 1]

H₂N-(E)_e-NH₂

In the above formula 1, the above formula (ii),

e may be selected from substituted or unsubstituted divalent C₆-C₃₀Aliphatic cyclic group, substituted or unsubstituted divalent C₄-C₃₀Heteroaliphatic cyclic group, substituted or unsubstituted divalent C₆-C₃₀Aromatic cyclic group, substituted or unsubstituted divalent C₄-C₃₀Heteroaromatic cyclic group, substituted or unsubstituted C₁-C₃₀Alkyl/alkylidene, substituted or unsubstituted C₂-C₃₀Alkenyl/alkenylene, substituted or unsubstituted C₂-C₃₀Alkynyl/alkynylene, -O-, -S-, -C (═ O) -, -ch (oh) -, -S (═ O)₂-、-Si(CH₃)₂-、-C(CH₃)₂-and-C (CF)₃)₂-。

e is an integer selected from 1 to 5. When E is 2 or more, E may be the same as or different from each other.

(E) in the above formula 1_eMay be selected from the group represented by the following formulas 1-1a to 1-14 a.

Specifically, (E) in the above formula 1_eMay be selected from the group represented by the following formulas 1-1b to 1-13b, but is not limited thereto.

More specifically, (E) in the above formula 1_eMay be a group represented by the above formula 1-6 b.

In one embodiment, the dianhydride compound may comprise a compound having a fluorine-containing substituent. Alternatively, the dianhydride compound may consist of a compound having a fluorine-containing substituent. In this case, the fluorine-containing substituent may be a fluorinated hydrocarbon group, and specifically may be a trifluoromethyl group, but is not limited thereto.

In another embodiment, a diamine compound may be used as the diamine compound. That is, the diamine compound may be composed of a single component.

For example, the diamine compound may include 2,2 '-bis (trifluoromethyl) -4,4' -diaminobiphenyl (TFDB) represented by the following formula, but is not limited thereto.

The dianhydride compound is a compound having a low birefringence value, and therefore it can contribute to enhancement of optical properties such as light transmittance of a polyamideimide film.

The dianhydride compound is not particularly limited, but it may be, for example, an aromatic dianhydride compound containing an aromatic structure. For example, the aromatic dianhydride compound may be a compound represented by the following formula 2.

[ formula 2]

In formula 2 above, G may be bonded through a bonding group selected from: substituted or unsubstituted tetravalent C₆-C₃₀Aliphatic cyclic group, substituted or unsubstituted tetravalent C₄-C₃₀Heteroaliphatic cyclic group, substituted or unsubstituted tetravalent C₆-C₃₀Aromatic cyclic group, substituted or unsubstituted tetravalent C₄-C₃₀A heteroaromatic cyclic group (wherein the aliphatic cyclic group, the heteroaliphatic cyclic group, the aromatic cyclic group or the heteroaromatic cyclic group may be present alone or may be bonded to each other to form a condensed ring), a substituted or unsubstituted C₁-C₃₀Alkyl/alkylidene, substituted or unsubstituted C₂-C₃₀Alkenyl/alkenylene, substituted or unsubstituted C₂-C₃₀Alkynyl/alkynylene, -O-, -S-, -C (═ O) -, -ch (oh) -, -S (═ O)₂-、-Si(CH₃)₂-、-C(CH₃)₂-and-C (CF)₃)₂-。

G in the above formula 2 may be selected from the group represented by the following formulae 2-1a to 2-9a, but is not limited thereto.

For example, G in the above formula 2 may be a group represented by the above formula 2-8 a.

In another embodiment, the dianhydride compound may consist of a single component or a mixture of two components.

For example, the aromatic dianhydride compound may include 2,2' -bis (3, 4-dicarboxyphenyl) hexafluoropropane dianhydride (6-FDA) represented by the following formula, but is not limited thereto.

The diamine compound and the dianhydride compound may be polymerized to form a polyamic acid.

Subsequently, the polyamic acid may be converted into a polyimide by a dehydration reaction, and the polyimide includes an imide repeating unit.

The polyimide may form a repeating unit represented by the following formula a.

[ formula A ]

In formula a above, E, G and e are as described above.

For example, the polyimide may include a repeating unit represented by the following formula A-1, but is not limited thereto.

[ formula A-1]

In the above formula A-1, n is an integer of 1 to 400.

The dicarbonyl compound is not particularly limited, but it may be, for example, a compound represented by the following formula 3.

[ formula 3]

In formula 3 above, J may be selected from substituted or unsubstituted divalent C₆-C₃₀Aliphatic cyclic group, substituted or unsubstituted divalent C₄-C₃₀Heteroaliphatic cyclic group, substituted or unsubstituted divalent C₆-C₃₀Aromatic cyclic groupSubstituted or unsubstituted divalent C₄-C₃₀Heteroaromatic cyclic group, substituted or unsubstituted C₁-C₃₀Alkyl/alkylidene, substituted or unsubstituted C₂-C₃₀Alkenyl/alkenylene, substituted or unsubstituted C₂-C₃₀Alkynyl/alkynylene, -O-, -S-, -C (═ O) -, -ch (oh) -, -S (═ O)₂-、-Si(CH₃)₂-、-C(CH₃)₂-and-C (CF)₃)₂-。

j is an integer selected from 1 to 5. When J is 2 or more, J may be the same as or different from each other.

X is a halogen atom. Specifically, X may be F, Cl, Br, I, etc. More specifically, X may be Cl, but is not limited thereto.

(J) in the above formula 3_jMay be selected from the group represented by the following formulas 3-1a to 3-14a, but is not limited thereto.

Specifically, (J) in the above formula 3_jMay be selected from the group represented by the following formulas 3-1b to 3-8b, but is not limited thereto.

More specifically, (J) in the above formula 3_jMay be a group represented by the above formula 3-2b or 3-3 b.

In one embodiment, a mixture of at least two dicarbonyl compounds different from each other may be used as the dicarbonyl compound. If two or more dicarbonyl compounds are used, at least two of (J) in the above formula 3 may be used_jA dicarbonyl compound selected from the group represented by the above formulas 3-1b to 3-8b is used as the dicarbonyl compound.

In another embodiment, the dicarbonyl compound may be an aromatic dicarbonyl compound containing an aromatic structure.

For example, the dicarbonyl compounds may comprise a first dicarbonyl compound and/or a second dicarbonyl compound.

The first dicarbonyl compound and the second dicarbonyl compound may each be an aromatic dicarbonyl compound.

The first dicarbonyl compound and the second dicarbonyl compound may be different compounds from each other.

For example, the first dicarbonyl compound and the second dicarbonyl compound may be aromatic dicarbonyl compounds different from each other, but are not limited thereto.

If the first dicarbonyl compound and the second dicarbonyl compound are each aromatic dicarbonyl compounds, they comprise a benzene ring. Therefore, they can contribute to the improvement of mechanical properties such as surface hardness and tensile strength of the polyamideimide film thus produced.

The dicarbonyl compound may include terephthaloyl chloride (TPC), 1 '-biphenyl-4, 4' -dicarbonyl dichloride (BPDC), or a combination thereof, represented by the following formula, but is not limited thereto.

For example, the first dicarbonyl compound may include BPDC and the second dicarbonyl compound may include TPC, but is not limited thereto.

Specifically, if BPDC is used as the first dicarbonyl compound and TPC is used in an appropriate combination as the second dicarbonyl compound, the polyamideimide film thus produced may have high oxidation resistance.

The diamine compound and the dicarbonyl compound may be polymerized to form a repeating unit represented by the following formula B.

[ formula B ]

In formula B above, E, J, e and j are as described above.

For example, the diamine compound and the dicarbonyl compound may be polymerized to form amide repeating units represented by the following formulas B-1 and B-2.

[ formula B-1]

In the above formula B-1, x is an integer of 1 to 400.

[ formula B-2]

In the above formula B-2, y is an integer of 1 to 400.

In another embodiment, the polymer solution may comprise a polyamideimide polymer formed by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound. In this case, the diamine compound may comprise one diamine compound, the dianhydride compound may comprise one dianhydride compound, and the dicarbonyl compound may comprise two dicarbonyl compounds.

Alternatively, the diamine compound may consist of one diamine compound, the dianhydride compound may consist of one dianhydride compound, and the dicarbonyl compound may consist of two dicarbonyl compounds.

As described above, the polyamideimide resin, which is a main component of the polyamideimide film, contains amide repeating units and imide repeating units as structural units in a predetermined molar ratio.

By properly controlling the contents of the imide repeating units and the amide repeating units, a polyamideimide film having good and balanced optical properties, mechanical properties and flexibility can be prepared without a complicated process. In addition, the polyamide imide film with good and balanced optical properties, mechanical properties and flexibility can be obtained without the need of the steps of precipitation, filtration, drying and redissolution, which are used in the prior art. The content of the imide repeating unit and the content of the amide repeating unit can be controlled by the amounts of the aromatic dianhydride compound and the dicarbonyl compound, respectively.

The molar ratio of imide repeat units to amide repeat units in the polyamideimide resin may be 20:80 to 80:20, for example 20:80 to 50: 50. In this case, the imide repeating unit may be a repeating unit represented by the above formula a, and the amide repeating unit may be a repeating unit represented by the above formula B.

If the molar ratio of the polyamideimide resins satisfies the above range, it is easy to control the viscosity of the polymer solution by preparing them using the monomers as described above. Thereby easily producing a uniform film without defects on the surfaces of the gel sheet and the cured film.

The organic solvent may be at least one selected from the group consisting of Dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), m-cresol, Tetrahydrofuran (THF), and chloroform. Specifically, in one embodiment, the organic solvent used in the polymerization solution may be dimethylacetamide (DMAc), but is not limited thereto.

Next, after the step of preparing the polymer solution, the polymer solution is transferred to a tank (S200).

FIG. 2 schematically illustrates process equipment for preparing a polyamideimide film according to one embodiment. Referring to fig. 2, a polymer solution as described above is prepared in a polymerization apparatus (10), and the polymer solution thus prepared is transferred and stored in a tank (20).

Here, once the polymer solution is prepared, the polymer solution is transferred to a tank without any additional step. Specifically, the polymer solution prepared in the polymerization apparatus is transferred and stored in a tank without any separate precipitation and re-dissolution steps to remove impurities. In the conventional method, in order to remove impurities such as hydrochloric acid (HCl) generated during the preparation of the polymer solution, the polymer solution thus prepared is purified by a separate step to remove the impurities, and then the purified polymer solution is redissolved in a solvent. However, in this case, there is a problem in that loss of the active ingredient is increased in the step of removing impurities, resulting in a decrease in yield.

Therefore, the manufacturing method according to one embodiment may reduce the amount of impurities finally generated in the step of preparing the polymer solution, or may appropriately control impurities in the subsequent step (even if a certain amount of impurities is present) so as not to deteriorate the physical properties of the finally obtained film. Thus, the method has an advantage in that a thin film is prepared without a separate precipitation or re-dissolution step.

The tank (20) is where the polymer solution is stored before it is formed into a film, and its internal temperature may be-20 ℃ to 20 ℃.

Specifically, the internal temperature may be-20 ℃ to 15 ℃, -20 ℃ to 10 ℃, -20 ℃ to 5 ℃, or-20 ℃ to 0 ℃, but is not limited thereto.

If the temperature of the tank (20) is controlled within the above range, the polymer solution can be prevented from deteriorating during storage, and the moisture content can be reduced, thereby preventing defects of the film produced therefrom.

The method for preparing the polyamideimide thin film may further include vacuum degassing the polymer solution transferred to the tank (20).

After the internal pressure of the tank is depressurized to 0.1 to 0.7 bar, vacuum degassing may be performed for 30 minutes to 3 hours. Vacuum degassing under these conditions can reduce bubbles in the polymer solution. Thereby, surface defects of the film thus produced can be prevented and excellent optical properties such as haze can be obtained.

In addition, the method for preparing the polyamideimide thin film may further include purging the polymer solution transferred to the tank (20) with an inert gas (S300).

Specifically, the purging is performed by purging the tank with an inert gas under an internal pressure of 1atm to 2 atm. The nitrogen purge under these conditions can remove moisture from the polymer solution, reduce impurities to improve reaction yield, and achieve excellent optical properties (e.g., haze) and mechanical properties.

The vacuum degassing step and the step of purging the tank with nitrogen are each performed in separate processes.

For example, a vacuum degassing step may be performed first, followed by a step of purging the tank with nitrogen, but is not limited thereto.

The vacuum degassing step and/or the step of purging the tank with nitrogen can improve the physical properties of the surface of the polyamideimide film thus produced.

Thereafter, the method may further include storing the polymer solution in the tank (20) for 12 hours to 360 hours. Here, the temperature in the tank may be maintained at-20 ℃ to 20 ℃.

The method of preparing the polyamideimide film may further include casting the polymer solution in the tank and then drying it to prepare a gel sheet (S400).

The polymer solution can be cast onto a casting body, for example a casting roll or a casting belt.

Referring to fig. 2, in one embodiment, the polymer solution may be applied to a casting belt (30) as a casting body and dried while moving to make a sheet in a gel form.

When the polymer solution is injected onto the belt (30), the injection amount may be 300g/min to 700 g/min. If the injection amount of the polymer solution satisfies the above range, the gel sheet can be uniformly formed to an appropriate thickness.

In addition, the casting thickness of the polymer solution may be 200 μm to 700 μm. If the polymer solution is cast to a thickness within the above range, the final film produced after drying and heat treatment may have a suitable and uniform thickness.

The polymer solution is dried at a temperature of 60 to 150 ℃ for 5 to 60 minutes after being cast to prepare a gel sheet. The solvent of the polymer solution is partially or completely volatilized during the drying process to prepare a gel sheet.

As described above, the viscosity of the polymer solution at room temperature may be 100000cps to 500000cps, for example, 100000cps to 400000cps, 100000cps to 350000cps, 100000cps to 300000cps, or 150000cps to 350000 cps. If the viscosity satisfies the above range, the polymer solution can be cast onto the belt to a uniform thickness without defects.

The method of preparing the polyamideimide thin film includes heat-treating the gel sheet while it is moving to prepare a cured film (S500).

Referring to fig. 2, the heat treatment of the gel sheet may be performed by passing it through a thermosetting device (40).

The heat treatment of the gel sheet may be performed at a temperature range of 80 ℃ to 500 ℃ at a temperature rise rate of 2 ℃/min to 80 ℃/min for 5 minutes to 40 minutes. Specifically, the heat treatment of the gel sheet may be performed at a temperature range of 80 ℃ to 470 ℃ for 5 minutes to 30 minutes at a temperature rising rate of 10 ℃/min to 80 ℃/min.

In this case, the initial temperature of the heat treatment of the gel sheet may be 80 ℃ or more, and the maximum temperature of the heat treatment may be 300 ℃ to 500 ℃. For example, the maximum temperature of the heat treatment may be 350 ℃ to 500 ℃, 380 ℃ to 500 ℃, 400 ℃ to 500 ℃, 410 ℃ to 480 ℃, 410 ℃ to 470 ℃, or 410 ℃ to 450 ℃.

That is, referring to fig. 2, the inlet temperature of the thermosetting device (40) may be an initial temperature of the heat treatment, and the temperature of a certain region within the thermosetting device (40) may be a maximum temperature of the heat treatment.

The heat treatment under these conditions can cure the gel sheet to have appropriate surface hardness and modulus while ensuring high light transmittance and low haze of the cured film.

The method for preparing the polyamideimide thin film includes cooling the cured film while it is moving (S600).

Referring to fig. 2, the cooling of the cured film is performed after it passes through the thermosetting apparatus (40). The cooling of the solidified film may be performed by using a separate cooling chamber (not shown) or by forming an appropriate temperature atmosphere without a separate cooling chamber.

The step of cooling the cured film while it is moving may include a first cooling step of reducing the temperature at a rate of 100 to 1000 ℃/min and a second cooling step of reducing the temperature at a rate of 40 to 400 ℃/min.

In this case, specifically, the second temperature decreasing step is performed after the first temperature decreasing step. The cooling rate of the first cooling step may be faster than the cooling rate of the second cooling step.

For example, the maximum rate of the first cool down step is faster than the maximum rate of the second cool down step. Alternatively, the minimum rate of the first cooling step is faster than the minimum rate of the second cooling step.

If the cured film is cooled in such a multistage manner, the physical properties of the cured film can be further stabilized, and the optical and mechanical properties of the film achieved during the curing step can be made more stable over a long period of time.

The moving speed of the gel sheet and the moving speed of the cured film are the same.

The method for preparing the polyamideimide film includes winding the cooled cured film using a winder (S700).

Referring to fig. 2, the cooled cured film may be wound by using a roll winder (50).

In this case, the ratio of the moving speed of the gel sheet on the belt at the time of drying to the moving speed of the cured film at the time of winding is 1:0.95 to 1: 1.40. Specifically, the ratio of the moving speed may be 1:0.99 to 1:1.20, 1:0.99 to 1:1.10, or 1:1.10 to 1:1.05, but is not limited thereto.

If the ratio of the moving speeds is outside the above range, the mechanical properties of the cured film may be impaired, and the flexibility and elastic properties may be deteriorated.

In particular, the speed of movement of the gel sheet on the belt during drying may be 0.1m/min to 15m/min, such as 0.5m/min to 10 m/min.

In the method for preparing a polyamideimide film, the thickness variation (%) according to the following formula 1 may be 3% to 30%, for example, 5% to 20%.

[ formula 1]

Thickness change (%) - (M1-M2)/M2X 100

In formula 1 above, M1 is the thickness (μ M) of the gel sheet, and M2 is the thickness (μ M) of the solidified film cooled upon winding.

The polyamideimide film prepared according to the above preparation method has high oxidation resistance and can secure excellent optical properties such as high light transmittance, low haze and low Yellow Index (YI). In addition, long-term stable mechanical properties can be achieved on flexible substrates requiring modulus, elongation, tensile properties and elastic restoring force.

In addition, in the conventional production method of the polyamideimide thin film, a by-product such as hydrochloric acid (HCl) is generated at the time of polymerization reaction. After passing through separate precipitation, filtration and drying steps to remove these by-products, the resultant is dissolved again in a solvent to prepare a composition for forming a film. However, when such precipitation, filtration, drying and redissolution steps are carried out, there is a problem that the yield is significantly reduced. In contrast, in the preparation method according to one embodiment, the polymer solution is not subjected to separate precipitation, filtration, drying and redissolution steps. Since the polymer solution prepared in the polymerization step can be directly applied to the casting step, the productivity can be remarkably improved.

In addition, in the conventional production method of a polyamideimide thin film, a nitrogen purge step is employed in the heat treatment for forming the film to ensure the transparency of the film and prevent yellowing thereof. In contrast, in the production method according to one embodiment, excellent optical properties can be obtained even without performing nitrogen purging in the film formation and heat treatment steps. Therefore, it is possible to eliminate the possibility of impurity doping during the manufacturing process or the possibility of damaging other physical properties other than the optical properties.

The polyamideimide film prepared by the preparation method as described above has excellent optical and mechanical properties. The polyamideimide film may be suitably used for various applications requiring flexibility and transparency. For example, the polyamideimide thin film may be applied to solar cells, displays, semiconductor devices, sensors, and the like.

The polyamideimide film may have a total light transmittance of 80% or more. Specifically, the total light transmittance of the polyamideimide film may be 80% to 99%. For example, it may be 85% to 99% or 88% to 99%.

The polyamide imide film may have a haze of 3% or less. For example, the haze may be 2% or less, or 1% or less.

The polyamideimide film may have a modulus in the MD direction of 5GPa to 10GPa when measured at room temperature. For example, the modulus may be 6GPa to 10GPa or 7GPa to 10 GPa. In addition, the modulus in the TD direction may be 5GPa to 10GPa or 6GPa to 10 GPa.

When the polyamideimide film is perforated at a rate of 10mm/min using a 2.5mm spherical tip in a UTM compression mode, the maximum diameter (mm) of the perforation including the crack is 60mm or less. Specifically, the maximum diameter of the perforations may be 5 to 60mm, 10 to 60mm, 15 to 60mm, 20 to 60mm, 25 to 60mm or 25 to 58mm, but is not limited thereto.

The polyamide-imide film has a compressive strength of 0.4 kgf/mu m or more. Specifically, the compressive strength may be 0.45kgf/μm or more, or 0.46kgf/μm or more, but is not limited thereto.

The polyamide-imide film has a yellowness index of 5 or less. Specifically, the yellow index may be 3 or less, 2.9 or less, 2.7 or less, 2.5 or less, 2.3 or less, 2.2 or less, or 2.1 or less, but is not limited thereto.

The surface hardness of the polyamide-imide film is HB or more. Specifically, the surface hardness may be H or more, or 2H or more, but is not limited thereto.

The tensile strength of the polyamideimide film was 15kgf/mm²The above. Specifically, the tensile strength may be 18kgf/mm²Above, 20kgf/mm²Above, 21kgf/mm²Above, or 22kgf/mm²The above is not limited thereto.

The polyamide-imide film has an elongation of 15% or more. Specifically, the elongation may be 16% or more, 17% or more, or 17.5% or more, but is not limited thereto.

The various properties of the polyamideimide films described above may be combined.

The physical properties of the polyamideimide film as described above are based on a thickness of 40 to 60 μm. For example, the physical properties of polyamideimide films are based on a thickness of 50 μm. In addition, "MD direction" refers to the direction in which the tape moves during the production of the film, and "TD direction" refers to the direction perpendicular to the MD direction.

The properties of the polyamideimide film as described above are the specific achievement results of the combination of chemical and physical properties of the components constituting the polyamideimide film under the conditions in each step of the method of preparing the polyamideimide film as described above.

Hereinafter, the above will be described in detail by referring to examples. The following examples are intended to illustrate the invention and the scope of the examples is not limited thereto.

Examples

For examples 1 to 6 and comparative example 1, each raw material component was prepared according to the composition shown in table 1.

[ Table 1]

Example 1

Dimethylacetamide (DMAc) as an organic solvent was added at 20 ℃ under a nitrogen atmosphere to a 1000 liter polymerization apparatus equipped with a temperature-controlled double jacket. Then, 2 '-bis (trifluoromethyl) -4,4' -diaminobiphenyl (TFDB) was slowly added thereto as an aromatic diamine and dissolved.

Subsequently, 2' -bis (3, 4-dicarboxyphenyl) hexafluoropropane dianhydride (6-FDA) was slowly added thereto as an aromatic dianhydride while the mixture was stirred for 1 hour.

Then, 1 '-biphenyl-4, 4' -dicarbonyl dichloride (BPDC) was added as a first dicarbonyl compound, and then the mixture was stirred for 1 hour. Terephthaloyl chloride (TPC) was added as a second dicarbonyl compound, and then the mixture was stirred for 1 hour, thereby preparing a first polymer solution.

The viscosity of the first polymer solution thus prepared was measured. If the measured viscosity did not reach the target viscosity, a 10 wt% TPC solution was prepared in DMAc organic solvent and 1ml of TPC solution was added to the first polymer solution, and the mixture was stirred for 30 minutes. This process was repeated until the viscosity reached 200000cps, thereby preparing a second polymer solution.

The second polymer solution was transferred to a tank and stored at-10 ℃. The tank was degassed for 1.5 hours to bring the pressure in the tank to 0.3 bar. Then, the tank was purged with nitrogen gas under an internal pressure of 1.5 atm. While purging, the second polymer solution was stored in the tank for 30 hours.

Subsequently, the second polymer solution was cast and then dried in hot air at 80 ℃ for 30 minutes, thereby preparing a gel sheet. Then, the gel sheet is heat-treated at a temperature rising rate of 2 to 80 ℃/min for 30 minutes in a temperature range of 80 to 500 ℃ while moving. Thereafter, the first temperature reduction step is carried out by reducing the temperature at a rate of 800 ℃/min, and then the second temperature reduction step is carried out by reducing the temperature at a rate of 100 ℃/min, thereby obtaining the polyamideimide film. The film was wound up by a winder. In this case, the moving speed of the gel sheet on the belt at the time of drying was 1 m/s. The speed of the winder is controlled so that the ratio of the moving speed of the gel sheet on the belt at the time of drying to the moving speed of the film at the time of winding is in the range of 1:1.01 to 1: 1.10.

Example 2

A film was prepared in the same manner except that the prepared second polymer solution was transferred and stored in a tank maintained at 0 ℃.

Example 3

A film was prepared in the same manner except that the prepared second polymer solution was transferred and stored in a tank maintained at 30 ℃.

Example 4

A film was produced in the same manner as in example 1 except that "a step of storing the second polymer solution in a tank for 30 hours" was not performed after the purging of the second polymer solution.

Example 5

A film was produced in the same manner as in example 1 except that the step of "degassing for 5 hours so that the pressure in the tank was 0.3 bar" was performed, and the step of "degassing for 1.5 hours so that the pressure in the tank was 0.3 bar" was not performed.

Example 6

A film was produced in the same manner as in example 1 except that the step of "degassing for 1.5 hours so that the pressure in the tank was 0.3 bar" was not performed after purging the second polymer solution.

Comparative example 1

A film was prepared in the same manner as in example 1, except that the step of "purging the tank with nitrogen" was not performed after the second polymer solution was transferred into the tank.

Evaluation examples

The following properties of the films according to examples 1 to 6 and comparative example 1 were measured and evaluated, respectively.

Evaluation example 1: measurement of film thickness

The thickness was measured at 5 points in the width direction using a digital micrometer 547-. The average value of these was taken as the thickness.

Evaluation example 2: measurement of light transmittance

The light transmittance at 550nm was measured using a haze meter NDH-5000W manufactured by Nippon Denshoku Kogyo.

Evaluation example 3: measurement of haze

The haze was measured using a haze meter NDH-5000W manufactured by Nippon Denshoku Kogyo.

Evaluation example 4: measurement of yellowness index

The Yellowness Index (YI) was measured with a spectrophotometer (UltraScan PRO, Hunter Associates Laboratory) using the CIE colorimetric system.

Evaluation example 5: measurement of modulus

The sample was cut at least 5cm in the direction perpendicular to the primary shrinkage direction of the film and 10cm in the primary shrinkage direction. In the universal test machine UTM 5566A from Instron, it is held by clamps arranged at 5cm intervals. The sample was stretched at 5mm/min at room temperature until breaking, and a stress-strain curve was obtained. The slope of stress with respect to the initial strain in the stress-strain curve is taken as the modulus (GPa).

Evaluation example 6: measurement of elongation

The sample was cut at least 5cm in the direction perpendicular to the primary shrinkage direction of the film and 10cm in the primary shrinkage direction. In the universal test machine UTM 5566A from Instron, it is held by clamps arranged at 5cm intervals. The sample was stretched at 5mm/min at room temperature until breaking, and a stress-strain curve was obtained. The maximum elongation at break in the stress-strain curve is defined as the elongation (%).

Evaluation example 7: measurement of tensile Strength

The sample was cut at least 5cm in the direction perpendicular to the primary shrinkage direction of the film and 10cm in the primary shrinkage direction. In the universal test machine UTM 5566A from Instron, it is held by clamps arranged at 5cm intervals. The sample was stretched at 5mm/min at room temperature until breaking, and a stress-strain curve was obtained. The maximum force applied at break in the stress-strain curve is defined as the tensile strength (kgf/mm)²)。

[ Table 2]

	Example 1	Example 2	Example 3	Example 4	Example 5	Example 6	Comparative example 1
								Thickness (μm)	50	50	50	50	50	50	50
Light transmittance (%)	89.8	89.7	89.7	88.9	89.7	88.9	88.7
								Haze (%)	0.53	0.55	0.58	0.86	0.56	1.25	1.04
Yellow Index (YI)	2.56	2.59	2.62	3.23	2.60	2.78	3.17
								Modulus (GPa)	6.10	6.08	6.02	5.36	5.23	4.36	5.15
Elongation (%)	11.53	11.72	11.62	10.42	8.54	3.22	8.29
								Tensile Strength (kgf/mm)²)	19.61	19.60	19.60	18.51	18.17	15.64	16.60

As can be seen from table 2 above, the production methods of examples 1 to 6 enable the production of polyamideimide films excellent in optical properties and mechanical properties, as compared with the production method of comparative example 1.

Description of the marks

10: polymerization plant

20: pot for storing food

30: belt

40: thermosetting device

50: winding machine

Claims

1. A method for preparing a polyamideimide film, comprising:

mixing and reacting a diamine compound, a dianhydride compound, and a dicarbonyl compound simultaneously or sequentially in an organic solvent in a polymerization apparatus to prepare a polymer solution;

transferring the polymer solution to a tank; vacuum degassing after transferring the polymer solution into the tank, wherein vacuum degassing is performed for 30 minutes to 3 hours after depressurizing the internal pressure of the tank to 0.1 to 0.7 bar;

purging the tank with an inert gas;

casting the polymer solution in the tank onto a belt and then drying it to prepare a gel sheet;

heat-treating the gel sheet while it is moving to prepare a cured film;

cooling the solidified film while it is moving; and

winding the cooled cured film with a winder,

wherein the step of preparing the polymer solution comprises:

(a) mixing and reacting a diamine compound, a dianhydride compound, and a dicarbonyl compound simultaneously or sequentially in an organic solvent to prepare a first polymer solution;

(b) measuring the viscosity of the first polymer solution and evaluating whether a target viscosity of 100000cps to 500000cps at room temperature is reached; and

(c) if the viscosity of the first polymer solution does not reach the target viscosity, a dicarbonyl compound is further added to produce a second polymer solution having the target viscosity.

2. The method of preparing a polyamideimide film according to claim 1, wherein the target viscosity is 100000cps to 300000cps at room temperature.

3. The method for producing a polyamideimide film according to claim 1, further comprising: in the step of preparing the polymer solution, the tank is purged with an inert gas.

4. The method for preparing a polyamideimide film according to claim 1, wherein once the polymer solution is prepared, the polymer solution is transferred to a tank without any additional step.

5. The method for producing a polyamideimide film according to claim 1, wherein the internal temperature of the can is-20 ℃ to 20 ℃.

6. The production method of a polyamideimide thin film according to claim 1, wherein the purging is to purge the can with an inert gas under an internal pressure of 1atm to 2 atm.

7. The method of preparing a polyamideimide thin film according to claim 1, further comprising storing the polymer solution in the tank for 12 hours to 360 hours after the purging step.

8. The method for preparing a polyamideimide film according to claim 1, wherein the polymer solution is dried at a temperature of 60 ℃ to 150 ℃ for 5 minutes to 60 minutes after being cast to prepare the gel sheet.

9. The method for preparing a polyamideimide film according to claim 1, wherein the heat treatment is performed at a temperature range of 80 ℃ to 500 ℃ at a temperature rising rate of 2 ℃/min to 80 ℃/min for 5 to 40 minutes.

10. The method for preparing a polyamideimide film according to claim 9, wherein the initial temperature of the heat treatment of the gel sheet is 80 ℃ or more and the maximum temperature of the heat treatment is 300 ℃ to 500 ℃.

11. The method for producing a polyamideimide film according to claim 1, wherein the step of cooling the solidified film while it is moving comprises:

a first temperature reduction step in which the temperature is reduced at a rate of 100 to 1000 ℃/min, and

a second cooling step, wherein the temperature is reduced at a rate of 40 ℃/min to 400 ℃/min in the second cooling step;

the second cooling step is carried out after the first cooling step; and

the cooling rate of the first cooling step is faster than that of the second cooling step.

12. The process for producing a polyamideimide film according to claim 1, wherein the ratio of the moving speed of the gel sheet on the belt at the time of drying to the moving speed of the cured film at the time of winding is 1:0.95 to 1: 1.40.

13. The method for producing a polyamideimide film according to claim 1, wherein the thickness variation according to the following formula 1 is 3% to 30%:

[ formula 1]

Thickness change (%) - (M1-M2)/M2X 100

In formula 1 above, M1 is the thickness of the gel sheet, and M2 is the thickness of the cooled cured film upon winding.

14. A polyamideimide film produced by the production method as set forth in claim 1.